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Chasing p0031 code in 04 grand cherokee, 4.0

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Hi all- have an 04 4.0 with the cali emissions, 4 o2 sensors. I recently got the p0031 code and assumed that the heater element in my b1s1 o2 was bad- so i replaced it with NTK o2 sensor . It came back the next day. What's weird is that I will let the jeep idle from a cold start for a minute and watch the fuel systems enter closed loop- but then when I begin driving, it enters OL-fault and throws the light. Other times, it will throw the code immediately upon starting (cold).
I am now trying to figure out where to go from here. I have tested the power to the fuse with a probe, power there. I even cut the heater wires from the old one, plugged it in, and tested the voltage to them with a multimeter- I got 13v at the one wire, and nada at the other. Am I doing anything wrong here in my diagnosing, or missing anything important? And if not, am I now looking at an intermittent break somewhere in the circuit? Any help would be greatly appreciated, I am losing my mind a little bit
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If your scan tool has the ability to perform a pcm relearn you should try it, if not disconnect the battery for 30 minutes and hook it back up and take it for a drive. That code is hard to clear out of the KAM on these after repairing the fault.
 

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Discussion Starter · #6 ·
If your scan tool has the ability to perform a pcm relearn you should try it, if not disconnect the battery for 30 minutes and hook it back up and take it for a drive. That code is hard to clear out of the KAM on these after repairing the fault.
I have had the battery disconnected many times the past week as i tried to get the code cleared. I will try to do it again, and see if my scanner has the ability to do this. Do you mean disconnecting both terminals? I have just disconnected the negative while trying to do this
 

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I have had the battery disconnected many times the past week as i tried to get the code cleared. I will try to do it again, and see if my scanner has the ability to do this. Do you mean disconnecting both terminals? I have just disconnected the negative while trying to do this
Yes, disconnect both terminals. I noticed in your other reply it's been intermittent so I don't hold much hope for it to work, I'd be looking for an issue in the circuit itself.

Do some continuity checks, tug / wiggle wires where you can.
 

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Discussion Starter · #9 ·
Yes, disconnect both terminals. I noticed in your other reply it's been intermittent so I don't hold much hope for it to work, I'd be looking for an issue in the circuit itself.

Do some continuity checks, tug / wiggle wires where you can.
Thanks, will do. How do i trace the heater lines back? They disappear into the fuel rail about six inches after the connector.
 
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